Effect of 30Bi₂O₃–55B₂O₃–15ZnO glass content on sintered copper paste for metallization of α-Al₂O₃ ceramics

Copper pastes are widely used in metallization of ceramic surfaces but are limited by poor oxidation resistance, high resistivity, and low bonding strength. In this work, the 30Bi₂O₃–55B₂O₃–15ZnO glass powder was prepared by the melt-quenching method. A copper paste containing the glass powder and formic acid-treated copper microparticles was used for metallization of α-Al₂O₃ ceramic surface. The copper thick films were obtained by low-temperature sintering after screen printing. The effects of the glass powder contents on resistivities and shear strengths of the copper films on α-Al₂O₃ ceramic substrate were analyzed. The microstructures of the copper thick films and the interfacial bonding mechanism on the α-Al₂O₃ ceramic surface were investigated in detail. The copper thick film with 10-wt% 30Bi₂O₃–55B₂O₃–15ZnO glass and sintered at 650 °C for 20 min exhibited a low resistivity (3.38 ± 0.94 µΩ cm) and a high shear strength (35.24 ± 1.2 MPa). ZnAl₂O₄ and Bi₂B₄O₉ were detected on the edges of the copper film near the interface, which enhanced interfacial binding between the copper thick films and the α-Al₂O₃ ceramic substrate. These results demonstrated that the low-temperature sintering copper paste containing 30Bi₂O₃–55B₂O₃–15ZnO glass was effective for α-Al₂O₃ ceramic surface metallization.